Fix mode index use case in vp9_pick_inter_mode
Fix mode index use case in vp9_pick_inter_mode

This improves coding performance of speed -5 and -6 by 0.6%,
respectively.

Change-Id: Ic5a7746a88c73285f0b14333d35dc16b02152c25

mbebenita/aom,mwgoldsmith/vpx,jacklicn/webm.libvpx,Suvarna1488/webm.libvpx,Acidburn0zzz/webm.libvpx,running770/libvpx,webmproject/libvpx,mbebenita/aom,shareefalis/libvpx,VTCSecureLLC/libvpx,gshORTON/webm.libvpx,GrokImageCompression/aom,zofuthan/libvpx,jdm/libvpx,jacklicn/webm.libvpx,felipebetancur/libvpx,Topopiccione/libvpx,mbebenita/aom,hsueceumd/test_hui,ittiamvpx/libvpx-1,luctrudeau/aom,running770/libvpx,lyx2014/libvpx_c,shareefalis/libvpx,pcwalton/libvpx,shyamalschandra/libvpx,ittiamvpx/libvpx-1,shyamalschandra/libvpx,pcwalton/libvpx,lyx2014/libvpx_c,goodleixiao/vpx,stewnorriss/libvpx,mwgoldsmith/libvpx,lyx2014/libvpx_c,liqianggao/libvpx,stewnorriss/libvpx,matanbs/webm.libvpx,mwgoldsmith/vpx,shacklettbp/aom,Acidburn0zzz/webm.libvpx,felipebetancur/libvpx,ShiftMediaProject/libvpx,reimaginemedia/webm.libvpx,mbebenita/aom,GrokImageCompression/aom,kleopatra999/webm.libvpx,luctrudeau/aom,liqianggao/libvpx,Maria1099/webm.libvpx,abwiz0086/webm.libvpx,Acidburn0zzz/webm.libvpx,liqianggao/libvpx,smarter/aom,webmproject/libvpx,felipebetancur/libvpx,VTCSecureLLC/libvpx,kalli123/webm.libvpx,Distrotech/libvpx,GrokImageCompression/aom,liqianggao/libvpx,hsueceumd/test_hui,Acidburn0zzz/webm.libvpx,goodleixiao/vpx,luctrudeau/aom,mbebenita/aom,VTCSecureLLC/libvpx,Suvarna1488/webm.libvpx,jacklicn/webm.libvpx,ShiftMediaProject/libvpx,shareefalis/libvpx,mwgoldsmith/libvpx,iniwf/webm.libvpx,shyamalschandra/libvpx,Suvarna1488/webm.libvpx,ShiftMediaProject/libvpx,luctrudeau/aom,felipebetancur/libvpx,openpeer/libvpx_new,pcwalton/libvpx,mwgoldsmith/vpx,mwgoldsmith/vpx,mwgoldsmith/vpx,zofuthan/libvpx,zofuthan/libvpx,Acidburn0zzz/webm.libvpx,stewnorriss/libvpx,webmproject/libvpx,abwiz0086/webm.libvpx,mbebenita/aom,jacklicn/webm.libvpx,kalli123/webm.libvpx,openpeer/libvpx_new,Maria1099/webm.libvpx,mwgoldsmith/libvpx,matanbs/vp982,zofuthan/libvpx,Acidburn0zzz/webm.libvpx,pcwalton/libvpx,matanbs/webm.libvpx,goodleixiao/vpx,shacklettbp/aom,thdav/aom,smarter/aom,openpeer/libvpx_new,thdav/aom,VTCSecureLLC/libvpx,reimaginemedia/webm.libvpx,gshORTON/webm.libvpx,shacklettbp/aom,abwiz0086/webm.libvpx,jdm/libvpx,zofuthan/libvpx,Distrotech/libvpx,lyx2014/libvpx_c,lyx2014/libvpx_c,thdav/aom,Maria1099/webm.libvpx,pcwalton/libvpx,kalli123/webm.libvpx,ittiamvpx/libvpx-1,matanbs/vp982,felipebetancur/libvpx,matanbs/webm.libvpx,Distrotech/libvpx,goodleixiao/vpx,altogother/webm.libvpx,iniwf/webm.libvpx,kleopatra999/webm.libvpx,ittiamvpx/libvpx-1,charup/https---github.com-webmproject-libvpx-,kalli123/webm.libvpx,hsueceumd/test_hui,zofuthan/libvpx,shyamalschandra/libvpx,GrokImageCompression/aom,GrokImageCompression/aom,charup/https---github.com-webmproject-libvpx-,Topopiccione/libvpx,abwiz0086/webm.libvpx,Distrotech/libvpx,jdm/libvpx,hsueceumd/test_hui,pcwalton/libvpx,shacklettbp/aom,matanbs/vp982,luctrudeau/aom,Topopiccione/libvpx,mbebenita/aom,kim42083/webm.libvpx,running770/libvpx,felipebetancur/libvpx,kim42083/webm.libvpx,stewnorriss/libvpx,luctrudeau/aom,liqianggao/libvpx,Suvarna1488/webm.libvpx,webmproject/libvpx,hsueceumd/test_hui,jacklicn/webm.libvpx,Topopiccione/libvpx,gshORTON/webm.libvpx,matanbs/vp982,mwgoldsmith/vpx,ittiamvpx/libvpx-1,Suvarna1488/webm.libvpx,shyamalschandra/libvpx,matanbs/vp982,gshORTON/webm.libvpx,liqianggao/libvpx,smarter/aom,altogother/webm.libvpx,gshORTON/webm.libvpx,GrokImageCompression/aom,mwgoldsmith/libvpx,Distrotech/libvpx,Laknot/libvpx,mwgoldsmith/libvpx,abwiz0086/webm.libvpx,shareefalis/libvpx,charup/https---github.com-webmproject-libvpx-,jmvalin/aom,kim42083/webm.libvpx,Laknot/libvpx,kleopatra999/webm.libvpx,Laknot/libvpx,altogother/webm.libvpx,smarter/aom,openpeer/libvpx_new,jdm/libvpx,altogother/webm.libvpx,shacklettbp/aom,reimaginemedia/webm.libvpx,kleopatra999/webm.libvpx,Topopiccione/libvpx,charup/https---github.com-webmproject-libvpx-,openpeer/libvpx_new,Topopiccione/libvpx,ittiamvpx/libvpx-1,Suvarna1488/webm.libvpx,shacklettbp/aom,Laknot/libvpx,iniwf/webm.libvpx,Maria1099/webm.libvpx,charup/https---github.com-webmproject-libvpx-,ShiftMediaProject/libvpx,kleopatra999/webm.libvpx,webmproject/libvpx,webmproject/libvpx,thdav/aom,shareefalis/libvpx,jacklicn/webm.libvpx,jmvalin/aom,jmvalin/aom,stewnorriss/libvpx,hsueceumd/test_hui,abwiz0086/webm.libvpx,Laknot/libvpx,iniwf/webm.libvpx,matanbs/webm.libvpx,jmvalin/aom,ShiftMediaProject/libvpx,goodleixiao/vpx,kleopatra999/webm.libvpx,goodleixiao/vpx,VTCSecureLLC/libvpx,running770/libvpx,matanbs/webm.libvpx,shareefalis/libvpx,Laknot/libvpx,openpeer/libvpx_new,jdm/libvpx,lyx2014/libvpx_c,altogother/webm.libvpx,reimaginemedia/webm.libvpx,mwgoldsmith/libvpx,iniwf/webm.libvpx,Maria1099/webm.libvpx,kalli123/webm.libvpx,matanbs/vp982,running770/libvpx,altogother/webm.libvpx,VTCSecureLLC/libvpx,kim42083/webm.libvpx,gshORTON/webm.libvpx,jmvalin/aom,reimaginemedia/webm.libvpx,thdav/aom,jmvalin/aom,stewnorriss/libvpx,mbebenita/aom,shyamalschandra/libvpx,matanbs/vp982,matanbs/webm.libvpx,smarter/aom,charup/https---github.com-webmproject-libvpx-,reimaginemedia/webm.libvpx,running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